Wireless communication has been a major area of research in recent years. Worldwide proliferation of wireless devices, such as mobile phones has led to emergence of several new technologies in this domain. Modulation of signals for wireless communication is one such area where new technologies and improvements over existing techniques are coming up at a rapid pace.
FIG. 1 is a block diagram illustrating a known polar modulator. Modern communication systems, such as the Universal Mobile Telecommunications System (UMTS) make use of polar modulation for modulating the baseband signals. An existing technique for implementing polar modulation is shown in FIG. 1.
In-phase (I) and quadrature (Q) baseband signals are applied to a COordinate Rotation DIgital Computer (CORDIC) 102, which converts the baseband signals into corresponding polar components: an amplitude signal 104 and a phase signal 106.
The amplitude signal 104 is passed through a Digital to Analog Converter (DAC) 108 that converts the digital amplitude signal 104 into a corresponding analog signal. The analog signal is then passed through an analog filter 110, which removes the signal components that are beyond a certain frequency offset from the analog signal. The phase signal 106 is passed through a Phase Locked Loop (PLL) 112, which maintains constant phase of the input signal. The output from the analog filter 110 and the output from the Phase Locked Loop 112 are combined together at a mixer 114, and are sent to an amplifier 116 for amplification. The amplified signal is then sent to a power amplifier 118 to ensure power efficiency. Thereafter the signal is transmitted via an antenna 120.
The polar modulator described above is generally implemented using silicon chip technology. The analog filters that are employed in polar modulators do not shrink as well as the digital components when the silicon structures achieve miniaturization. Furthermore, each of the analog filters fabricated on the chip have to be matched to each other. In other words, each of the filters would need to have the same gain in order to avoid differential non-linearity. Achieving this can be difficult in semiconductor implementation.